Car Will Not Start problems of the 2008 Mercedes Benz GL450

Vehicle caught fire in my garage. Vehicle was running fine 2 hrs prior. My husband entered the vehicle to run an errand and the vehicle would not start. Tons of light came on the dash, including the airbag had deployed, though the airbag had not deployed. Vehicle was off but still sounded like it was running. Windows or nothing would work. We raised the hood and was not able to discover the issue. We could smell something, but was not sure what it was. We proceeded to go inside our home, but left the garage and hood open so the smell from the vehicle would leave the garage. Couple hours later we heard a hissing sound in the garage. My husband went outside and discovered the truck on fire. Not sure where it started, when saw it was underneath the vehicle. We extinguished the fire but the fire dept was called out. Fire dept sound like an electrical issue. This could have been deadly had we not heard the sound and had the garage door open. My insurance company has been contacted.